Surface Water and Stray Gas

Shallow Aquifer Contamination

Avner Vengosh, Nathaniel Warner, Robert Jackson,

Tom Darrah

Nicholas School of Environment,

Duke University

Technical Workshop on Case Studies to Assess

Potential Impacts of Hydraulic Fracturing on Drinking Water Resources

July 30, 2013

The approach of the Duke study:

• Conduct field-base studies in areas associated with shale gas

development; search for temporal and spatial water-quality

variations;

• Evaluate the geochemistry of groundwater from the associated

aquifers; define the major geochemical features that characterize

groundwater and surface water prior to shale gas development.

• Link possible water contamination to changes in water chemistry

using multiple geochemical and isotopic tracers as proxies for

sources and mechanisms of water contamination (using a single

constitute in water as an evidence for, or lack of contamination, is

misleading!).

• Integrate advanced geochemical and isotopic tools with

hydrogeology.

• Evaluate the solid-phase (aquifer rocks, river sediments) and

possible impact on water quality by using laboratory experiments).

1. Since 2010 sampling over 600 shallow private wells in PA, NY,

WV, AK, NC, TX;

2. Sampling produce/flowback waters from the Marcellus Shale

and conventional oil and gas wells from PA and NY;

3. Sampling over 100 surface waters in PA and river sediments

downstream from waste waters disposal sites;

3. Analysis of methane geochemistry in private wells –

concentrations, ratios (ethane/methane), isotopes ( 13CCH4,

2HCH4)

4. Analysis of the chemistry (major and trace elements) and

isotopes (87Sr/86Sr, 11B, 18O, 2H, 13C-DIC)

5. Measurements of naturally occurring radium (226Ra, 228Ra)

radionuclides;

6. Measurement of noble gases in groundwater.

Research conducted as part of the Duke study:

Structure of the Duke study:

Water quality

Shale gas exploration

Hydrocarbon

Geochemistry 13C-CH4,

C1/C2

Aquatic

Geochemistry 87Sr/86Sr, 11B,

18O, 2H,

Noble gas

geochemistry

Groundwater Surface water/

river sediments

Aquatic

Geochemistry

Isotopes 87Sr/86Sr, 11B,

18O, 2H,

Radionuclides 228Ra/226Ra

Possible impact

Duke Study - Results

• Evidence for tray gas contamination in a subset of shallow wells near (<1 km) shale gas wells in northeastern PA (Osborn et al., 2011, Jackson et al., 2013).

• Evidence for natural flow of saline groundwater to shallow aquifers in in northeastern PA; indication to hydraulic connectivity to deep geological formations, but no indication to water contamination (Warner et al., 2012).

• Lack of stray gas and water contamination of shallow groundwater in Arkansas (Warner et al., 2013).

• Evidence for surface water contamination downstream from shale gas wastewater disposal site in western PA; accumulation of radium in river sediments (Warner et al., in review).

The debate on stray gas contamination

No risk:

Methane is ubiquitous in

groundwater, with higher

concentrations observed in

valleys vs. upland; methane

concentrations are best correlated

to topographic and hydrogeologic

features, rather than shale-gas

extraction (Molofsky et al.,

2013).

High risk in a subset of wells

near shale gas sites :

Evidence for stray gas

contamination in a subset of wells

less than a km from shale gas

sites in northeastern PA (Osborn

et al., 2011; Jackson et al., 2013;

Darrah et al., 2012).

Duke Study: northeastern PA

Definition of active versus non-active wells: Private wells located <1km from a shale gas had typically higher methane

(Osborn et al., 2011; PNAS, 108,8172-8176 )

Reinforcement of the data:

(Jackson et al., 2013; PNAS, June 2013)

Presence of ethane and propane

in wells <1 km from nearest gas

well must be derived from

thermogenic source that occurs

in shale gas wells (no ethane and

propane in biological gas)

Methane sources?

Closer to shale gas wells higher

methane higher 13CCH4 lower

CH4/HC ratios

(Jackson et al., 2013; PNAS, June 2013)

A distinction between a natural

background methane flow and direct

stray gas contamination

GROUNDWATER IN

FAYETTEVILLE SHALE

NORTH-CENTRAL

ARKANSAS

Warner et al., (2013); Applied

Geochemistry, May 2013

0

5

10

15

20

25

30

0 5 10 15

Dis

solv

ed

Met

han

e (

mg-

CH

4/L

)

Distance to nearest natural gas well (km)

Low TDS

Ca-HCO3

Na-HCO3

Cl>20 mg/L

Potential Action Level

Warner et al., (2013); Applied Geochemistry, May 2013

No evidence for stay gas contamination in Arkansas

Occurrence of saline groundwater enriched in

barium in shallow aquifers

Occurrence of saline groundwater enriched in

barium in shallow aquifers

Warner et al., 2012, PNAS, July 2012

Upper Devonian brines

Marcellus brines

Geochemical and isotopic evidence for mixing with Marcellus brines

Warner et al., 2012, PNAS, July 2012

Disposal of wastewater from shale gas

development

Warner et al., 2013, ES&T (in review)

Josephine Brine Treatment Facility

Warner et al., 2013, ES&T (in review)

Brine treatment has no effect on halogens

Radium occurrence in flowback and produced

waters from the Marcellus Shale

Source: Duke University

Radiation threshold

(requires a licensed

radioactive waste

disposal facility)

A long-term legacy of radioactivity accumulation in river

sediments associated with a disposal site (Josephine, PA)

Warner et al., 2013, ES&T (in review)

Conclusions:

• Evidence for methane contamination in shallow drinking water wells

in some locations in northeastern Appalachian Basin (PA) but not in

Fayetteville Basin (AK).

•No evidence has shown, so far, for direct groundwater contamination

from produced/flowback water; yet we show evidence for hydraulic

connectivity between the Marcellus and shallow aquifers in PA.

• Disposal of produced water from gas exploration directly into surface

water poses a significant risks to water resources and long-term

radioactivity hazard. A zero-discharge policy is recommended.

• Sustainable and long-term shale gas developments will need to

accommodate the environmental issues associated with shale gas

drilling and hydro-fracturing.

Acknowledgements

• Nicholas School of Environment, Duke University

• National Science Foundation, Geobiology & Low-Temperature

Geochemistry Program

• Park Foundation.

For more information:

http://sites.nicholas.duke.edu/avnervengosh/

References

Warner, N.R., Christie, C.A., Jackson. R.B., Vengosh, A. (2013) Impacts of shale gas wastewater disposal on water

quality in western Pennsylvania. Environmental Science & Technology (in review).

Jackson, R.B., Vengosh, A., Darrah, T.H., Warner, N.R., Down, A., Poreda, R.J., Osborn, S.G., Zhao, K., and Karr,

J.D. (2013) Increased stray gas abundance in a subset of drinking water wells near Marcellus shale gas extraction.

Proceedings of the National Academy of Sciences of United States of America (in press, June, 2013).

Warner N.R., Kresse, T.M., Hays, P.D., Down, A., Karr, J.D., Jackson, R.B., Vengosh, A. (2013) Geochemical and

isotopic variations in shallow groundwater in areas of Fayetteville Shale development, north central Arkansas.

Applied Geochemistry (http://dx.doi.org/10.1016/j.apgeochem.2013.04.013).

Warner, N.R., Jackson, R.B., Darrah, T.H., Osborn, S.G., Down, A., Zhao, K., White, A. Vengosh, A. (2012).

Geochemical evidence for possible natural migration of Marcellus formation brine to shallow aquifers in

Pennsylvania. Proceedings of the National Academy of Sciences of United States of America. (July 9, 2012, doi:

10.1073/pnas.1121181109).

Osborn, S., Vengosh, A. Warner, N. Jackson, R. (2011). Methane contamination of drinking water accompanying gas

drilling and hydro-fracking. Proceedings of the National Academy of Sciences of United States of America, 108,

8172-8176.